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Linting ROS 2 Packages with mypy

#linter   #ros2   #mypy  

Table of Content

Linting ROS 2 Packages with mypy#

linter, is a static code analysis tool used to flag programming errors, bugs, stylistic errors and suspicious constructs.

mypy is an optional static type checker for Python that aims to combine the benefits of dynamic (or “duck”) typing and static typing

python hinting#

Type hints are performed using Python annotation They are used at add types to variables function arguments and return values,
Python hinting has no runtime effect they only use for static analyses with tools like mypy and help ide’s to help us with more information and intellisense

Post from Python tutorial: Introduction to Python type hints

hinting demo
from typing import List
from typing import Union

number = Union[int, float]

def get_list(item: number) -> List[number]:
    list = [1, 2, item]
    return list

print(get_list(1.0))

VSCode#

Config mypy

setting.json
"python.linting.mypyEnabled": true,
"python.linting.mypyCategorySeverity.error":"Warning",
"python.linting.mypyArgs": [
    "--ignore-missing-imports"
]

ROS2 linting#

The ament_lint metapackage defines many common linters that can integrate into the build/test pipeline for ROS 2. The package ament_mypy within handles mypy integration

install#

sudo apt install ros-humble-ament-cmake-mypy

mypy demo#

  • Config package.xml
  • Edit setup.py
  • Add TestCase

package.xml#

  • Add entry
<test_depend>ament_mypy</test_depend>

setup.py#

Add / Edit line

tests_require=['pytest']

TestCase#

test_mypy.py
from ament_mypy.main import main

import pytest


@pytest.mark.mypy
@pytest.mark.linter
def test_mypy():
    rc = main()
    assert rc == 0, 'Found code style errors / warnings'

Run (colcon test)#

colcon test --packages-select <YOUR_PACKAGE> --event-handlers console_direct+

mypy ini#

mypy ini read the doc for more settings

ROS2 ament mypy

ini file location at test folder for colcon test

mypy.ini
[mypy]
ignore_missing_imports = True

ignore_missing_imports#

Suppresses error messages about imports that cannot be resolved.

show_column_numbers#

Shows column numbers in error messages.

Reference#